Oral Mucosa Notes

Oral Mucosa

Learning Objectives

  • Identify and describe the general structure of mucosal surfaces in the body.

  • Compare and contrast the structure of mucosa with other lining epithelia like skin.

  • Compare the microscopic structure of oral cavity mucosa with the GIT (gastrointestinal tract) mucosa regarding their functions.

  • Demonstrate knowledge of oral cavity anatomy, including features of the vestibule and oral cavity proper regions.

  • Show knowledge of the structure and function of different types of oral mucosa (classified by function: masticatory, lining, and specialized).

  • Compare and contrast the types of epithelium from different regions of the oral cavity (keratinized vs. non-keratinized, orthokeratinized vs. parakeratinized).

What is Oral Mucosa?

  • Oral mucosa is a mucous membrane, which are moist linings of body cavities that communicate with the exterior.

  • Examples of locations: oral cavity, nasal passages, pharynx, GIT, and urogenital tract (UGT).

Oral Mucosa Details

  • Oral mucosa is a mucous membrane that's a moist lining of the oral cavity.

  • Structurally, it resembles skin and other mucous membranes like those in the esophagus, cervix, and vagina.

  • It is notably different from GIT mucosa.

Mucous Membrane Functions

  • Mucous membranes are moist linings of body cavities that communicate with the exterior.

  • They line various cavities/lumens in the body and cover the surface of internal organs.

  • Functions include:

    • Protection of underlying tissues.

    • Prevention of dehydration.

    • Prevention of pathogen entry.

    • Prevention of particulate matter entry.

Mucosa Layers

  1. Epithelium

  2. Lamina propria:

    • Underlying connective tissue.

    • Loose papillary layer.

    • Dense reticular layer.

  3. Muscularis mucosa:

    • Only present in GIT.

    • Not present in oral tissues.

Comparison of Epithelial Linings

  • Oral mucosa is structurally similar to skin, esophagus, cervix, and vagina.

  • It differs significantly from GIT mucosa.

Mucosa Barrier Function

  • Epithelium:

    • Protection (physical/mechanical, chemical, and cellular).

  • Lamina propria:

    • Protection (cellular/immune defense).

    • Ground substance (attachment, mechanical).

  • Muscularis mucosa:

    • Absent in oral mucosa.

Nomenclature of Layers: Oral Coverings vs. Skin

  • Oral mucosa:

    • Epithelium.

    • Lamina propria (papillary & reticular layers).

    • Submucosa (not always present).

  • Skin:

    • Epidermis.

    • Dermis (papillary & reticular layers).

    • Hypodermis.

Functions of Oral Mucosa

Function

Structures Involved

Protection

Epithelium (stratum corneum)

Friction/abrasion

Mechanical role

Compression/shearing

Lamina propria (collagen/elastin)

Barrier role

Epithelium (superficial barrier), Molecules

Taste

Epithelium (taste buds)

Sensory

Epithelium & lamina propria (sensory receptors)

Synthesis/secretion

Saliva (minor salivary glands in lamina propria/submucosa)

Esthetics

Vermilion border of lips, Sebaceous glands (lamina propria)

Anatomy of the Oral Cavity

  • Structures include:

    • Teeth, gingiva (gum).

    • Hard palate, soft palate, uvula.

    • Tongue, tonsil.

    • Buccal mucosa (lip and cheek lining).

    • Floor of mouth, lip.

Oral Cavity Definition

  • The oral cavity extends from the lips to the pharynx and contains the tongue and teeth.

  • Two parts:

    1. Vestibule:

      • Space between the lips/cheeks (labial & buccal).

    2. Oral cavity proper:

      • Enclosed by teeth.

      • Contains the hard & soft palates and the mouth floor.

Oral Mucosa Lining - Vestibule

  • Attached gingiva.

  • Alveolar mucosa.

  • Lining mucosa.

  • Vermillion zone.

  • Adjoining labial mucosa.

  • Secretions from minor salivary glands.

Types of Oral Mucosa (Classified by Function)

  • Masticatory mucosa: 25% of total area.

  • Lining mucosa: 60% of total area.

Masticatory vs. Lining Mucosa

  • Masticatory mucosa (mucoperiosteum):

    • Epithelium, lamina propria, and bone.

  • Lining mucosa:

    • Epithelium and lamina propria.

Types of Keratinization

A. Keratinization:
* Keratinization Subtypes
* Orthokeratinization
* Parakeratinization

B. Non-keratinization:
* Buccal mucosa

Parakeratinized vs. Orthokeratinized Epithelium

  • Parakeratinized epithelium:

    • Similar to keratinized epithelium, except cell nuclei are present in the keratinized layer (stratum corneum).

    • Present in the oral cavity, specifically the gingiva.

    • Outside of the oral cavity it's considered a pathology.

  • Orthokeratinized epithelium:

    • Normal keratinized epithelium.

    • Present in skin or the outer part of the lip.

Comparison of Stratified Epithelium

A. Orthokeratinized epithelium:
* Keratinized layer.
* Granular layer.
* Prickle cell layer.
* Basal cell layer.

B. Parakeratinized epithelium:
* Keratinized layer.
* Granular layer.
* Prickle cell layer.
* Basal cell layer.

C. Nonkeratinized epithelium:
* Superficial layer.
* Intermediate layer.
* Prickle cell layer.
* Basal cell layer.

Oral Cavity Mucosa

  • Lining mucosa:

    • Present on the lips, buccal mucosa, alveolar mucosa, soft palate, underside of the tongue, and floor of the mouth.

    • Epithelium is usually nonkeratinized.

  • Masticatory mucosa:

    • Hard palate and gingiva regions.

    • Specialized mucosa on the dorsum of the tongue.

    • Inflexible, tough, resistant to abrasion, and tightly bound to the lamina propria.

    • Covered by a layer of keratinized cells (except sulcular and junctional).

Gingival Mucosa - Dentogingival Junction

  • Papillary layer of lamina propria.

  • Enamel space.

  • Free gingiva.

  • Junctional epithelium (attaches to enamel).

  • Attached gingiva (tooth, below to bone).

Oral Mucosa Orientation

  • Includes structures such as:

    • Vermillion border, hairy skin.

    • Gingiva, enamel, dentine, pulp, cementum.

    • Free gingiva, attached gingiva, alveolar mucosa.

    • Gingival margin, gingival groove, mucogingival junction.

    • Gingival crevice/sulcus.

    • Junctional epithelium.

    • Periodontal membrane.

    • Skeletal muscle.

    • Root canal, apical foramen.

    • Alveolar bone, body of mandible.

    • Cementoenamel junction.

What's Below the Mucosa?

  • Submucosa:

    • Present in cheeks, lips, and hard palate.

    • Contains adipose/glandular tissue, nerves, and blood vessels.

    • Direct attachment to bone in some places (oral mucosa, gingiva, parts of hard palate) directly to periosteum.

    • Submucosa is absent leading to firm inelastic attachment

    • Desmosomes.

    • Hemidesmosomes.

    • Tonofilaments.

    • Gap & tight junctions.

Lining Mucosa

  • Non-keratinized stratified squamous epithelium.

  • Locations:

    • Lips.

    • Buccal mucosa.

    • Alveolar mucosa.

    • Soft palate.

    • Underside of the tongue.

    • Floor of the mouth.

Masticatory Mucosa (Summary)

  • Keratinized stratified squamous epithelium.

  • Locations:

    • Hard palate.

    • Attached gingiva.

    • Dorsum of tongue.

  • Areas of repeated mechanical exposure/physical damage exhibit distinct resistance to deformation under load, abrasion, thermal, and chemical damage.

Questions to Consider

  • What is a mucosa?

  • What are the structural & functional differences between lining mucosa & masticatory mucosa?

  • How does the mucosa function as a barrier?

  • What is the difference between orthokeratinised & parakeratinised epithelium?

  • How is oral mucosa classified by function?

References

  • Mescher AL Junquiera’s Basic Histology McGraw-Lange 13thEd

  • Kerr JB Atlas of Functional Histology

  • Nanci A. Ten Cate’s Oral Histology Development Structure and Function 6th Ed Mosby

  • Squier C & Brogden K 2011, Human Oral Mucosa Development, Structure & Function Wiley-Blackwell

  • Turabelidze A, Guo S, Chung AY, Chen L, Dai Y, Marucha PT, et al. (2014) Intrinsic Differences between Oral and Skin Keratinocytes. PLoS ONE 9(9): e101480. doi:10.1371/journal.pone.0101480 http://dx.doi.org/10.1371/journal.pone.0101480